"She will run for Chancellor," Norbert Roettgen said on Tuesday on CNN's "Amanpour."
"She is absolutely determined, willing, and ready to contribute to strengthen the international liberal order. But we can't see the Chancellor or Germany as last man standing."
"The Chancellor is a cornerstone of this political concept of the West as acting as a global player. So she will run, and she will act as a responsible leader," Roettgen said.
"But it would be impossible to rely only on one person. We need the West, and the West is indispensable.
"And this of course means fundamentally and indispensably also the participation and contribution of the strongest part of the West, and this is the United States of America."
Even though Merkel faces some backlash over Germany's Syrian refugee policies that have seen hundreds of thousands of refugees flock into the country, she remains favorite to win the election if she runs for fourth term as Germans want some stability in government following Donald Trump's U.S election victory,the Brexit vote in Britain and the rise of populist movements in Europe.